This has the aura of a homework question. So I will answer the question with more questions.

What is the programing environment of the router. Features, support libraries and limits.
Is it a real embedded system or a made up one?

Think of the purpose of a router. What is flowing through it. What info do these things carry. What additional information will you need to be able to implement routing functions the would not be attached to the items flowing through the router. Where can you get this info?